Description of the prior art
Fine-grained bean curd (so-called KINUKOSHI TOFU in Japanese) is generally manufactured in the following way namely, soybeans kept soaked in water are crushed and boiled and then soybean milk is obtained by separating bean curd refuse. Soybean milk thus obtained has a temperature of around 80.degree. C. This soybean milk of high temperature is mixed with a coagulating agent and is coagulated into fine-grained bean curd. Bean curd is classified into "filled bean curd" and "cut bean curd" according to the method of manufacturing the bean curd. In the case of filled bean curd, soybean milk of high temperature is cooled, is mixed with a coagulating agent, is poured into a pack of a size and a shape corresponding to one piece of bean curd, and the pack is sealed hermetically. The pack containing soybean milk is heated to such an extent that the soybean milk therein coagulates. In manufacturing the filled bean curd in the above way, the air which intermingles with soybean milk when soybean milk is put in a pack and is sealed hermetically produces air bubbles, when heating the soybean milk or with the lapse of time after filling. Such air bubbles float on the surface of soybean milk, and if soybean milk is coagulated in this state, bubbles are formed at the surface of bean curd. Presence of these bubbles will lower the commodity value of bean curd. In order to avoid forming such bubbles, a deaerator is used for letting the mixed-in air out of the soybean milk. Yet, perfect deaerating is impossible.
As compared with filled bean curd, in the case of cut bean curd soybean milk is coagulated in a coagulating box of the size corresponding to at least several pieces of bean curd and the coagulated piece is cut into several pieces of bean curd. In manufacturing the cut bean curd, when soybean milk is poured into a coagulating box air bubbles mingle with soybean milk but some of them get out of the soybean milk before the soybean milk coagulates, and bubbles are hardly formed at the surface of the bean curd.
Coarse-grained bean curd (so-called MOMEN TOFU in Japanese) is manufactured in the following way; namely, coagulated soybean milk is broken into many small blocks and such broken bean curd blocks are filled in a shaping box for pressing, dehydrating and shaping. Irrespective of whether manufacturing fine-grained bean curd or coarse-grained bean curd, calcium sulfate is generally used as a coagulating agent, but it has been known that the use of magnesium chloride (known as natural bittern) in place of calcium sulfate produces delicious bean curd. This natural bittern imparts a sweet flavor to bean curd for manufacturing of delicious bean curd and differs from calcium sulfate as to the temperature and speed at which soybean milk is coagulated. The coagulating speed with natural bittern is faster than that with calcium sulfate. Therefore, use of natural bittern for coagulating purposes is preferable and can safely be applied to manufacturing of coarsegrained bean curd. However, when using natural bittern for manufacturing fine-grained bean curd, it is necessary to cool down soybean milk to around 80.degree. C. before mixing natural bittern in it, because if natural bittern is mixed in soybean milk of high temperature, coagulation starts at once and uneven bean curd will result. However, from the viewpoint of productivity and other considerations, there is a limit to the soybean milk cooling down temperature. Therefore, in manufacturing fine-grained bean curd, it has been the usual practice to use natural bittern in the quantity about 10-20% of the total weight of coagulating agent used. Mixing of natural bittern at the ratio of more than 20% for manufacturing fine-grained bean curd causes uneven coagulation, with the resulting production of rather coarse-grained bean curd of less commodity value. Thus, mixing of more than 20% natural bittern for manufacturing fine-grained bean curd was impossible. Even when 20% natural bittern is mixed in, if a coagulating agent comprising 20% magnesium chloride and 80% calcium sulfate is mixed in soybean milk at one time, irregular coagulation occurs and, therefore in this case, magnesium chloride which is 20% of the total weight of the coagulating agent is first mixed in, and then 80% calcium sulfate is added. Thus, it takes more time and requires a greater number of steps to manufacture fine-grained bean curd by using natural bittern and that there is a limit in the quantity of natural bittern to be used. Therefore, although it is generally admitted that in manufacturing fine-grained bean curd, the more the quantity of natural bittern used, the more delicious the bean curd, there has been a limit in the quantity of natural bittern to be used for manufacturing of fine-grained bean curd.
Since fine-grained bean curd is soft and is very easy to break, when fine-grained bean curd manufactured in a specified shape is put piece by piece in a pack, such packing cannot be done in the air. It has therefore been a usual practice in packing fine-grained bean curd to soak fine-grained bean curd in water, have the worker dip up the curd carefully piece by piece out of the water by hand and put one piece each in a pack held by the other hand. Packs, each containing one piece of bean curd, are supplied to an automatic packing machine through a conveying means, such as a conveyor, or manually for wrapping up in a thin film, such as polyethylene film, and then shipped. Packing of bean curd is an indispensable operation for a bean curd manufacturer which manufactures bean curd in large quantities for wholesaling to super markets and retailers. However, given that fine-grained bean curd is soft and very easy to break as mentioned before, it is impossible to pack bean curd automatically or mechanically. For this reason, fine-grained bean curd is dipped up carefully out of the water in which it has been soaked and then is packed. This involves poor efficiency and requires many hands in a manufacturing process. Moreover, because bean curd is soaked in the water of in lukewarm water, sundry germs easily stick to the bean curd and there is the fear that such sundry germs propagate after seal-packing and bean curd itself does not keep long.